1st Quarter, 2009 Vol. 15, No. 1 ISSUED: January 22, 2009 A Quarterly Bulletin of the Pacific El Niño/Southern Oscillation Applications Climate (PEAC) Center Providing Information on Climate Variability for the U.S.-Affiliated Pacific Islands www.soest.hawaii.edu/MET/Enso CURRENT CONDITIONS The year of 2008 both began and ended with La Niña con- the year with near-normal rainfall. A series of storms through- ditions, with ENSO indices remaining neutral for most of the out November and December brought much-needed rainfall and year. But while the prevailing state of the climate was helped improve drought conditions to many areas of the state. ENSO-neutral, the weather patterns were far from normal. However, the excessive rainfall in December caused significant Climatic effects more typical of La Niña were noted for much of flooding across portions of Kauai and Oahu, producing severe 2008, and included well-known La Niña-related anomalies such damage to homes, infrastructure, and farm lands. One particu- as below normal tropical cyclone activity across most of Micro- larly strong thunderstorm produced a rare tornado as it made nesia, a weak monsoon, higher than normal sea-level, and abnor- landfall over the Pakala area of south Kauai on December 13. mally strong and widespread easterly surface winds in the low No typhoons directly affected any island in the central or latitudes. Oceanic cooling observed along the equator in the western North Pacific basin during 2008. In fact, until Typhoon central and eastern Pacific increased in magnitude in late 2008, Dolphin tracked past Guam in mid-December, the Guam nudging the climate back into La Niña by year’s end. Weather Forecast Office had issued no tropical cyclone watches During the calendar year 2008, the weather throughout or warnings in its area of responsibility. Guam and the CNMI the U.S.-Affiliated Pacific Islands (USAPI) was generally were placed under a tropical storm watch and a tropical storm tranquil, with no destructive wind events and few extremes warning as Dolphin passed by (rather uneventfully). of rainfall. However, the most dramatic climate extreme of Sea-level variation in the USAPI is sensitive to the ENSO- the year occurred during the week of December 8-15, 2008, cycle, with low sea-level observed during El Niño years and when an unusual pattern of gale-force winds located in the high sea-level during La Niña years. Sea-levels have been subtropics of the western North Pacific near the Interna- above normal since early 2007. Current forecasts indicate that tional Date Line generated oceanic swell that traveled to the sea-levels will remain elevated at all USAPI stations through the south and caused phenomenal surf throughout eastern Mi- next several months, as La Niña conditions continue to develop. cronesia and all the way south to the northern coast of The following comments were taken from WFO Guam’s Papua New Guinea (see page 12 for press release). Massive MONTHLY PACIFIC ENSO DISCUSSION FOR MICRONE- inundation was experienced in many locations, with damage to SIA AND AMERICAN SAMOA, issued in January 2009: infrastructure, personal property, and crops. Damages also oc- “The return to La Niña conditions will keep trade winds curred in the RMI, and a full investigation of the damages in all stronger and more persistent than normal. This will reinforce of the USAPI is now underway. The PEAC Center is committed the higher than normal sea-levels we have experienced in the to a thorough meteorological examination of this event, with a western Pacific, exposing most of the Micronesian islands, espe- special report to follow. cially the low islands, to periods of coastal flooding and inunda- The 2008 annual rainfall at most of the USAPI recording sites tion, particularly during full moon and new moon phases and was below normal (see Figures 1a and 1b). Annual rainfall to- during high surf episodes. This situation could last into early tals were less than 75% of normal at some of the atolls of the summer. Tropical cyclone activity will be pushed to the west, northern RMI, at Woleai in the southern part of Yap State, at reducing the risk of hurricanes to American Samoa and likely Polowat in the western portion of Chuuk State, at Kahului Air- delaying the Northern Hemisphere typhoon season for Microne- port on Maui, and on parts of Guam. Annual rainfall totals with sia. Rainfall in American Samoa will likely be below normal amounts below 70 inches occurred at Woleai, Saipan, Guam and due to reduced monsoon activity. The Republic of the Marshall in some of the northern atolls of the RMI. Annual rainfall totals Islands, and Yap State and Chuuk State in the FSM will likely exceeding 200 inches occurred on Pohnpei Island, Nukuoro, and have below normal rainfall for the next few months. The Kosrae. The 223.67 inches recorded at the Kosrae Airport was Marianas will experience high month-to-month rainfall variabil- the USAPI’s highest reported annual rainfall total during 2008. ity during its dry season. Pohnpei State will have near normal After a drier-than-normal October, the Hawaiian islands set- rainfall, while Kosrae State will have normal to above normal tled into a typical rainy season pattern, and most stations ended rainfall. Rainfall for Palau will also be normal to above normal.” Page 2 Pacific ENSO Update SEA SURFACE TEMPERATURES SOUTHERN OSCILLATION INDEX Sea Surface Temperatures (SST) From September 2008 – January 2009, negative sea-surface temperature (SST) anomalies strengthened and became more widespread in the central and eastern equatorial Pacific as La Niña conditions redeveloped. During the last 4-weeks, SSTs were at least 0.5°C be- low-average throughout the central and eastern equatorial Pacific Ocean, and more than 1°C below-average between 170°W and 110°W. According to the U.S. Climate Prediction Center (CPC), the latest weekly SST departures are -0.8ºC in Niño 4, -1.1ºC in Niño 3.4, - 0.9ºC in Niño 3, and -0.6ºC in Niño1+2. Positive SST anomalies covered much of the North Atlantic and west-central South Pacific Oceans, while negative anomalies were evident in a region extending from the west coast of North America to the Gulf of Alaska and Bering Sea. Southern Oscillation Index (SOI) The 3-month average of the Southern Oscillation Index for the 4th Quarter of 2008 was +1.4, with monthly values of +1.3, +1.5, and +1.5 for the months of October, November and December 2008, respectively. With the exception of May 2008 (when the monthly SOI value dipped down to –0.3), the SOI has been positive since August 2007. Normally, positive SOI values in excess of +1.0 are associ- ated with La Niña conditions, and negative SOI values below -1.0 are associated with El Niño conditions. The SOI is an index repre- senting the normalized sea level pressure difference between Darwin, Australia and Tahiti, respectively. 1a) 220 200 2008 Annual Rainfall 180 Total (Inches) . ) S 160 E H 140 C N I ( 120 L L 100 A F 80 N I A 60 R 40 20 0 i l l i o O u O a rt il n ta O B O d t O ir o i t e a n je O p e lu u lo g li S e ia o F F S n a k r g r t w i t a u l i a S e l o H A a w S li o n o o t le o S l h lu u H P W l W o p l in R W W l o W a u a p U a W a i o h e ir to T A s l k r r H j W p L n a o r P p W A i m k I o i P u a i s a o la g ro a p a m u a P e A u w r o K a Y n a a u T p N m il u g H o a u u n a e t K j in P K p C G h h g ra u a l i G C o in s a M A a P p o N S a K K 150 1b) 2008 Annual Rainfall . 125 Percent of Normal L A M R 100 O N F O 75 T N E C 50 R E P 25 0 i l l i o O u O a rt il n ta O B O d t O ir o i t e a n je O p e lu u lo g li S e ia o F F S n a k r g r t w i t a u l i a S e l o H A a w S li o n o o t le o S l h lu u H P W l W o p l in R W W l o W a u a p U a W a i o h e ir to T A s l k r r H j W p L n a o r P p W A i m k I o i P u a i s a o la g ro a p a m u a P e A u w r o K a Y n a a u T p N m il u g H o a u u n a e t K j in P K p C G h h g ra u a l i G C o in s a M A a P p o N S a K K Figure 1, above.